East Palo Alto's groundwater risk has vital lessons for The City

New research further magnifies the growing risk rising groundwater poses to San Francisco and other low-lying Bay Area cities.

The nonprofit think tank San Francisco Bay Area Planning and Urban Research Association and the East Palo Alto community organization Nuestra Casa released a study earlier this week analyzing the impacts groundwater rise could have on East Palo Alto.

The research centered on the Peninsula city because of its proximity to the water, making it one of the Bay Area jurisdictions most susceptible to groundwater rise. But the findings, researchers said, can be applied to all of the Bay Area’s at-risk cities — including San Francisco.

Coastal shallow groundwater is rainwater that is stored underground in soil, as opposed to ground water stored in aquifers used for drinking water and crop irrigation.

As sea levels rise due to climate change, coastal shallow groundwater is pushed up further towards the surface. The closer the groundwater table gets to the surface, the less capacity the soil has to absorb rain — and consequently, the more likely heavy precipitation will cause flooding, damage infrastructure and mobilize soil pollutants such as pesticides and asbestos.

“I think it’s a really important issue right now because we are making all of these plans and starting to do actual implementation projects around sea-level rise,” said SPUR’s Sarah Atkinson, who authored the study entitled “Look Out Below.” “But if we don’t consider groundwater rise, we could create other issues with the projects that we actually implement.”

SPUR’s analysis found that, without intervention, rising groundwater will increase inland flood risk in the eastern neighborhoods of East Palo Alto, damage local infrastructure, mobilize contaminants at longtime industrial sites — there are 50 such areas vulnerable to groundwater rise — and make the city’s buildings more susceptible to soil liquefaction during earthquakes.

Researchers said that with 2 feet of sea-level rise, as is projected over the next 70 years, groundwater levels will create flooding that will make it “difficult for residents to navigate neighborhoods east of Pulgas Avenue.” They also said homes could flood, which will increase the rates of mold and fungi growth and lead to unhealthy air quality.

In its policy recommendations for East Palo Alto, researchers advised the city to require all infrastructure plans to assess groundwater risk, update sea level rise and flood maps to reflect groundwater, and provide funding mechanisms to support groundwater research.

Atkinson said most of the findings and recommendations are relevant to San Francisco , another waterside city with buildings — including Financial District high-rises — left exposed to surging tides and groundwater.

The Port of San Francisco released a study earlier this year analyzing the effects coastal flooding and sea-level rise could have on the San Francisco waterfront. Atkinson said that while the report mentioned groundwater rise, the plan was broad and didn’t give any specifics about mitigating the issue.

She said she hopes SPUR’s study provides a direction and recommendations for how agencies like the San Francisco Public Utilities Commission, which manages The City’s water systems, can address groundwater rise.

Atkinson compared the demographics, geography and situation of East Palo Alto with San Francisco’s Bayview-Hunters Point neighborhood, because both are low-income communities which have been significantly impacted by environmental hazards. Hunters Point has been the site of a disjointed decadeslong effort to clean up radioactive toxins at a the former U.S. Navy shipyard in the neighborhood.

Contaminated areas such as Hunters Point are particularly at risk because of how flooding can move the toxins already present at the site to other areas. Sixty percent of East Palo Alto’s contaminated sites are already affected by high groundwater levels, SPUR’s study found.

“Groundwater just adds another burden on top of everything else,” Atkinson said.

The good news for The City, she said, has been moving in the right direction. In 2021, The City released a Hazards and Climate Resilience Plan in which it proposed almost 100 strategies to mitigate climate-change impacts. Among those were actionable steps to combat groundwater rise.

“San Francisco is thinking about this and is ahead of many other cities,” Atkinson said. “They’re positioned well to be able to take action on this.”